检索结果-南通市图书馆

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

整体叶轮圆角立铣刀五轴U摆线剥铣轨迹规划

机械工程学报 2024年第7期60卷 212-223页

作者：李佳男魏兆成冯景洋王学勤大连理工大学高性能精密制造全国重点实验室大连116024

摆线剥铣工艺具有加工效率高、切削力小、刀具耐用度高的优点,然而由于缺乏五轴剥铣加工的轨迹规划方法,导致高效剥铣技术难以应用于整体叶轮加工。针对该问题提出一种整体叶轮圆角立铣刀五轴U摆线剥铣的轨迹规划方法。安排系列切削力实... 详细信息

摆线剥铣工艺具有加工效率高、切削力小、刀具耐用度高的优点,然而由于缺乏五轴剥铣加工的轨迹规划方法,导致高效剥铣技术难以应用于整体叶轮加工。针对该问题提出一种整体叶轮圆角立铣刀五轴U摆线剥铣的轨迹规划方法。安排系列切削力实验,验证圆角立铣刀U摆线剥铣相较于现有球头立铣刀U摆线剥铣的加工优势。在此基础上建立叶轮模型降维映射关系,将三维叶根曲线映射到二维平面上,作为边界规划降维刀触点,基于刀触点与流道两侧叶片的比例关系计算刀轴矢量和刀位点,实现圆角立铣刀五轴U摆线剥铣轨迹初步规划。计算叶根过渡面上点到刀具特征面的距离,建立圆角立铣刀与叶根过渡面的干涉判据模型。使用投影法将干涉的叶根过渡面点集向刀轴矢量投影,计算刀具的最大轴向干涉量,从而优化刀位点排除叶根过渡面干涉。最后应用叶轮加工仿真验证五轴U摆线轨迹方法的有效性,结果表明五轴U摆线轨迹能够顺利实现整体叶轮圆角立铣刀剥铣加工,加工过程中无过切干涉,残留材料均匀,可为叶轮后续加工提供良好的基础。

关键词：摆线加工剥铣刀具轨迹叶根干涉

在线全文

学校读者我要写书评

暂无评论

基于降维映射的五轴U摆线铣削刀轨生成研究

机械工程学报 2024年第5期60卷 362-377页

作者：冯景洋魏兆成王敏杰舒鑫张勇雍建华大连理工大学精密与特种加工教育部重点实验室大连116024 沈阳鼓风机集团股份有限公司沈阳110869

刀具轨迹生成作为数控加工的重要组成部分,是包含铣削方式、刀具工件结构以及加工余量等多因素在内的复杂体系。U摆线铣削是在摆线铣削基础上结合侧铣加工特性的走刀策略,能够以大轴向切深完成粗加工,平稳切入切出的走刀形式可以有效平... 详细信息

刀具轨迹生成作为数控加工的重要组成部分,是包含铣削方式、刀具工件结构以及加工余量等多因素在内的复杂体系。U摆线铣削是在摆线铣削基础上结合侧铣加工特性的走刀策略,能够以大轴向切深完成粗加工,平稳切入切出的走刀形式可以有效平滑切削力,分散局部载荷。以整体叶轮流道为目标,提出一种基于降维映射的U摆线铣削刀轨生成方法。建立U摆线铣削几何模型,定义摆线表征参数并给出摆线残留量计算方法。根据刀具运动规律将轨迹离散为系列微元,以刀具与前一刀轨迹的交点为划分依据将轨迹划分为多个区域,分别获得相应摆线位置角下刀-工包角计算方法。安排了系列实验,验证了U摆线铣削在切削力及刀具磨损方面的加工优势。结合U摆线铣削特征建立铣削边界预处理方法,考虑到三维空间刀具轨迹计算复杂,定义空间几何域及降维参数域,在此基础上给出平铺微弧的降维映射方法并分别在不同摆线区间计算降维轨迹。为获得无干涉U摆线铣削刀轴矢量,借助等参数方程建立双向比例域映射算法,通过求解系列偏转角度实现任意矢量逆映射。最后将轨迹矩阵编码为通用机床语言,通过仿真算例及铣削实验验证刀轨生成方法的可行性。

关键词： U摆线铣削降维映射刀-工包角五轴铣削刀具轨迹

早强型粉煤灰改性土力学特性及强度预测模型分析

在线全文

学校读者我要写书评

暂无评论

建筑施工 2024年第4期46卷 471-475页

作者：任瀚马潇宇朱志男伍维强冯景阳中国建筑第八工程局有限公司甘肃兰州730100

由于硅酸盐水泥在生产过程中容易造成严重的资源消耗,因此粉煤灰常被用来部分替代水泥固化剂。但是粉煤灰由于自身的低活性,其改性土强度的形成,通常需要较长的养护周期。因此采用一种早强型粉煤灰基固化剂,通过一系列的无侧限抗压强度... 详细信息

由于硅酸盐水泥在生产过程中容易造成严重的资源消耗,因此粉煤灰常被用来部分替代水泥固化剂。但是粉煤灰由于自身的低活性,其改性土强度的形成,通常需要较长的养护周期。因此采用一种早强型粉煤灰基固化剂,通过一系列的无侧限抗压强度试验,探究了改性土无侧限抗压强度与固化剂掺量、养护龄期、改性土孔隙率等参数的变化规律。试验结果表明,早强型粉煤灰改性土7 d无侧限抗压强度可以达到28 d强度的80%~90%。基于试验结果,建立了基于孔隙率/掺量两个参数的强度预测公式,并进一步提出了预测公式的折减系数。

关键词：粉煤灰改性土早期强度力学特性强度预测

在线全文

学校读者我要写书评

暂无评论

风对砂土非饱和带水汽热运移规律影响研究

建筑施工 2024年第4期46卷 451-454页

作者：郭烨朱志男伍维强成昊凌冯景阳徐亮生中国建筑第八工程局有限公司甘肃兰州730100

针对目前以非饱和带土体水汽热运移对类似铁路、公路工程以及污染物运移影响根本认识不足的问题,基于室内砂土土柱试验,开展了在一定热辐射条件下,考虑风速(0、0.56、1.44 m/s)对砂土非饱和带水汽热运移规律影响研究。结果表明:温度控... 详细信息

针对目前以非饱和带土体水汽热运移对类似铁路、公路工程以及污染物运移影响根本认识不足的问题,基于室内砂土土柱试验,开展了在一定热辐射条件下,考虑风速(0、0.56、1.44 m/s)对砂土非饱和带水汽热运移规律影响研究。结果表明:温度控制系统和风速控制系统工作以后,风速的增大一方面降低了土表的温度梯度,并减缓着水分的流失,另一方面加快土表水分的流失作用,2种机制共同影响着土体的含水率变化。蒸发速率受到温度梯度的影响,随着温度梯度以及基质势作用下气态水向上运移速率趋于稳定,土体的瞬时蒸发量在40 h之后也趋于稳定。总结的经验可供今后类似项目借鉴。

关键词：风速地下水水位砂土非饱和带水热运移

Artificial optical microfingerprints for advanced anticounterfeiting

在线全文

学校读者我要写书评

暂无评论

Nano Research 2024年第5期17卷 4371-4378页

作者： Xueke Pang Qiang Zhang jingyang Wang Xin Jiang Menglin Wu Mingyue Cui Zhixia feng Wenxin Xu Bin Song Yao He Suzhou Key Laboratory of Nanotechnology and Biomedicine Institute of Functional Nano&Soft Materials&Collaborative Innovation Center of Suzhou Nano Science and Technology(NANO-CIC)Soochow UniversitySuzhou 215123China School of Sensing Science and Engineering Shanghai Engineering Research Center for Intelligent Diagnosis and Treatment InstrumentSchool of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Artificial optical microfingerprints,known as physically unclonable functions(PUFs)offer a groundbreaking approach for ***,these PUFs artificial optical microfingerprints suffer from a limited number of challenge-response pairs,making them vulnerable to machine learning(ML)attacks when additional error-correcting units are *** study presents a pioneering demonstration of artificial optical microfingerprints that combine the advantages of PUFs,a large encoding capacity algorithm,and reliable deep learning authentication against ML *** approach utilizes the triple-mode PUFs,incorporating bright-field,multicolor fluorescence wrinkles,and the topography of surface enhanced Raman scattering in the mechanical and optical ***,the quaternary encoding of these PUFs artificial microfingerprints allows for an encoding capacity of 6.43×10^(24082) and achieves 100%deep learning recognition ***,the PUFs artificial optical microfingerprints exhibit high resilience against ML attacks,facilitated by generative adversarial networks(GAN)(with mean prediction accuracy of~85.0%).The results of this study highlight the potential of utilizing up to three PUFs in conjunction with a GAN training system,paving the way for achieving encoded information that remains resilient to ML attacks.

关键词： artificial microfingerprints physically unclonable functions deep learning anti-counterfeiting

A Comparative Study of Machine Learning Models for Traffic Accident Severity Prediction on Rural Highways

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Traffic and Transportation Engineering(English Edition) 2024年

作者： fengxiang Guo jingyang Li feng Zhu Bijiang Tian Wenchen Yang School of Transportation Science and Engineering， Harbin Institute of Technology Yunnan Key Laboratory of Digital Communications National Engineering Research Center for Efficient Maintenance， Safety and Durability of Roads and Bridges，Broadvision Engineering Consultants Co.， Ltd Kunming Faculty of Transportation Engineering， Kunming University of Science and Technology School of Civil and Environmental Engineering， Nanyang Technological University

The use of machine learning models for analyzing Traffic Accident Severity (TAS) is increasingly common in safety assessment and traffic accident prevention. However， many existing studies have not fully considered the importance of feature engineering， model hyperparameter optimization， and training set proportions， all of which significantly affect the performance of these models. This study addresses the research gap by developing a TAS model using the Light Gradient Boosting Machine (LightGBM) and integrating two feature engineering methods (Random Forest (RF) and Principal Component Analysis (PCA)). Additionally， we compared the LightGBM with three other machine learning models: Support Vector Machine (SVM)， Binary Logistic Regression (BL)， and Deep Neural Network (DNN). This comparison evaluates the effectiveness of different machine learning approaches in classifying TAS， taking into account variations in feature engineering techniques and training set proportions. The case study examines rural highway accidents in Yunnan Province， China， focusing on three categories of factors influencing TAS: accident characteristics， traffic flow， and highway conditions. Moreover， the SHAP (SHapley Additive exPlanations) values were employed to identify the primary factors contributing to the accident severity. The results show that with the training set size of 80%， all four models achieve the highest predictive accuracy for severe accidents. Notably， the PCA+lightGBM combination model outperforms others in overall accident prediction accuracy and has the highest recall rate and F1 score for severe accidents. Comparing the four models under different feature inputs， the impact of feature selection on model performance is less significant than reducing the data heterogeneity. LightGBM and DNN are more susceptible to data heterogeneity， and improving data homogeneity markedly boosts the model’s performance. Through SHAP analysis， it is evident that the modes of transportati

关键词：

OsPPG encodes a pseudouridine-5'-phosphate glycosidase and regulates rice spikelet development

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

The Crop Journal 2024年第3期12卷 698-708页

作者： Rui Chen Dagang Tian Yarong Lin Jiaqing Huang Qinqin Yang Yupei Li Huaqing Liu Shaohua Yang jingyang Chen Shufen Zhou feng Wang Shubiao Zhang Key Laboratory of Genetics Breeding and Multiple Utilization of CropsMinistry of Education/Key Laboratory of Biological Breeding for Fujian and Taiwan CropsMinistry of Agriculture and Rural AffairsFujian Agriculture and Forestry UniversityFuzhou 350002FujianChina Fujian Key Laboratory of Genetic Engineering for Agriculture Biotechnology Research InstituteFujian Academy of Agricultural SciencesFuzhou 350003FujianChina Institute of Resources Environment and Soil FertilizerFujian Academy of Agricultural SciencesFuzhou 350013FujianChina

Florets are the basic structural units of spikelets,and their morphogenesis determines the yield and quality of rice ***,whether and how pseudouridine-5’-phosphate glycosidase participates in rice spikelet development remains an open *** this study,we identified a novel gene,OsPPG,which encodes a peroxisome-localized pseudouridine-5’-phosphate glycosidase and regulates the development of rice *** mutants exhibited abnormal sterile lemma,lemma,palea,lodicule,stamens,and pistils;male sterility;shorter panicles;and reduced plant *** was found to regulate several OsMADS genes,thereby affecting the morphogenesis of rice ***,metabolomics revealed that the OsPPG gene was involved in the decomposition of pseudouridine via the pyrimidine metabolism pathway and may affect the jasmonic acid signaling *** results suggest that OsPPG is a key regulator of rice spikelet development.

关键词： OsPPG Reproductive regulation Spikelet development Rice

METTL3-mediated m^(6)A modification of HMGA2 mRNA promotes subretinal fibrosis and epithelial-mesenchymal transition

在线全文

学校读者我要写书评

暂无评论

Journal of Molecular Cell Biology 2023年第3期15卷 1-17页

作者： Yuwei Wang Yuhong Chen Jian Liang Mei Jiang Ting Zhang Xiaoling Wan Jiahui Wu Xiaomeng Li Jieqiong Chen Junran Sun Yifan Hu Peirong Huang jingyang feng Te Liu Xiaodong Sun Department of Ophthalmology Shanghai General HospitalShanghai Jiao Tong University School of MedicineShanghai 200080China Shanghai Key Laboratory of Ocular Fundus Diseases Shanghai 200080China Shanghai Geriatric Institute of Chinese Medicine Shanghai University of Traditional Chinese MedicineShanghai 200031China National Clinical Research Center for Eye Diseases Shanghai 200080China Shanghai Engineering Center for Visual Science and Photomedicine Shanghai 200080China

Subretinal fibrosis is a major cause of the poor visual prognosis for patients with neovascular age-related macular degeneration(nAMD).Myofibroblasts originated from retinal pigment epithelial(RPE)cells through epithelial-mesenchymal transition(EMT)contribute to the fibrosis formation.N^(6)-Methyladenosine(m^(6)A)modification has been implicated in the EMT process and multiple fibrotic *** role of m^(6)A modification in EMT-related subretinal fibrosis has not yet been *** this study,we found that during subretinal fibrosis in the mouse model of laser-induced choroidal neovascularization,METTL3 was upregulated in RPE *** m^(6)A epitranscriptomic microarray and further verification,high-mobility group AT-hook 2(HMGA2)was identified as thekey downstream target of METTL3,subsequently activating potent EMT-inducing transcription factor ***,by subretinal injections of adeno-associated virus vectors,we confirmed that METTL3 deficiency in RPE cells could efficiently attenuate subretinal fibrosis in *** conclusion,our present research identified an epigenetic mechanism of METTL3-m^(6)A-HMGA2 in subretinal fibrosis and EMT of RPE cells,providing a novel therapeutic target for subretinal fibrosis secondary to nAMD.

关键词： METTL3 N^(6)-methyladenosine epithelial-mesenchymal transition subretinal fibrosis HMGA2

微小RNA-145-5p调控视网膜β-catenin对小鼠眼轴的影响

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

眼科学报 2018年第3期33卷 149-153页

作者：马明明冯竞仰上海市眼底病重点实验室上海市第一人民医院上海眼视觉与光医学工程技术研究中心上海200080

目的:探讨mi R-145-5p调控视网膜β-catenin表达对小鼠眼轴的影响。方法:取18只雄性3周龄C57BL/6小鼠按照随机数字表法随机分成对照组,miR-145-5pmimics组和miR-145-5p对照组。分组第2,5,8天双眼玻璃体腔注射1次药物,共注射3次:对照组... 详细信息

目的:探讨mi R-145-5p调控视网膜β-catenin表达对小鼠眼轴的影响。方法:取18只雄性3周龄C57BL/6小鼠按照随机数字表法随机分成对照组,miR-145-5pmimics组和miR-145-5p对照组。分组第2,5,8天双眼玻璃体腔注射1次药物,共注射3次:对照组小鼠玻璃体腔内注射3μL枸橼酸盐缓冲液,miR-145-5p mimics组小鼠玻璃体腔内注射3μL含有3μg miR-145-5p mimics的枸橼酸盐缓冲液,miR-145-5p对照组采取同样方法注射3μg miR-145-5p对照载体。最后一次注射完成3 d后A超测量小鼠眼轴长度,之后取小鼠视网膜组织,采用RT-PCR技术检测视网膜中miR-145-5p和β-catenin的表达,采用Western印迹法检测视网膜组织中β-catenin的含量。取6只成年雄性C57BL/6小鼠,构建β-catenin mRNA 3'UTR荧光素酶过表达载体,将β-catenin mRNA 3'UTR荧光素酶过表达载体与miR-145-5p mimics共同转染小鼠视网膜组织,3 d后取视网膜组织,应用荧光素酶报告基因技术检测和验证miR-145-5p与β-catenin的相关性。结果:视网膜转染miR-145-5p mimics后,小鼠眼轴长度降低,与对照组相比有显著性差异(P0.05);荧光素酶报告基因结果显示转染miR-145-5p和β-catenin mRNA 3'UTR荧光素酶过表达载体后,视网膜组织中荧光活性显著降低(P<0.001)。结论:miR-145-5p能够下调视网膜β-catenin的表达,进而控制眼轴增长。

关键词：微小RNA-145-5p 眼轴 Wnt/β-catenin通路荧光素酶报告基因技术